Vow Renewal Minister/Officiant

We need some advice about our upcoming Renewal. What is the customary fee/donation/gift that you would give to the minister who performs the service?? Not sure what is acceptable. Thanks for your help!

For our vow renewal last year we tipped the minister $50. We had forgotten to bring money with us to the ceremony (due to the jitters, I guess), so we told him we'd leave the tip with the wedding coordinators the next day. Luckily, the next morning when we went up to the wedding coordinator's office to leave the tip, we saw our minister there! He was getting ready to do a wedding. So we were able to tip him in person. I guess the moral of this story is, don't let the pre-ceremony jitters get to you; remember to bring the minister's tip money with you to the ceremony.